Melt spinning of modified cross section yarn



March 7, 1967 FELL 3,308,221

. T INNING F M SEC Original Filed May 14, 1963 INVENTOR. JAMES E. OPFELL BY RM 41 Hmm ATTORNEY United States Patent 3,308,221 MELT SPINNING 0F MODIFIED CROSS SECTION YARN James E Opfell, Colonial Heights, Va., assignor to Allied Chemical Corporation, New York, N.Y., a corporation 9f New York Original application May 14, 1963, Ser. No. 280,321, now Patent No. 3,216,186. Divided and this application Oct. 21, 1965, Ser. No. 511,011

3 Claims. (Cl. 264174) This is a division of application Serial No. 280,321, filed May 14, 1963 and now U.S. Patent 3,216,186.

This invention relates to novel multifilament thermoplastic yarns having improve-d visual appearance, and particularly to lustrous yarns of adjustable bulk consisting of a multitude of crirnped continuous filaments of novel cross sectional configuration, and to the production therefrom of tufted carpets.

In the production of high quality textile floor coverings such as rugs, carpets, and the like, it is generally sought to achieve good resiliency, high covering power, and resistance to soiling. Another quality frequently sought is a visual luster highlight or sparkling effect in the carpet surface. Securement of resiliency and covering power with continuous filament yarn has generally been sought by utilization of yarns having individual filaments of greater than about 7 denier, and wherein the texture or bulk of the yarn has been increased by crimping prior to incorporation into carpet structures. It is found however that yarns having the requisite bulk to produce good carpet characteristics do not process well in manufacturing operations such as tufting wherein the yarn must pass through narrow eyes of needles in the course of carpet manufacture.

It has been recognized that latent bulking characteristics may be imparted to carpet yarns by chemical or physical modification which develops mechanical crimping forces during carpet dyeing at elevated temperatures, to improve covering power and resiliency. Yarns having such latent propensity to become bulkier upon exposure to relaxing conditions of elevated temperature and no tensile restraint generally undergo a shrinkage with consequent increase in relaxed yarn denier. It has been found however, that although a certain amount of bulking produces desirable improvements in yarn covering power and carpet resiliency, an excessive amount of yarn shrinkage leads to undesirable loss of pile height, resulting in a matted carpet appearance frequently referred to as pull down.

Various filament cross sectional configurations have been employed to secure certain physical and asthetic property improvements in carpets. For example, central 1y symmetrical filaments having triangular or multilobal cross sectional configurations have been studied in efforts to secure improved carpet resiliency in view of the higher bending modulus or stiffness of said modified filaments. Cross sectional configurations containing straight portions in multi-vaned multi-lobed, or polygonal pattern have been studied in efforts to secure enhanced optical qualities such as reflectivity or luster highlight. Typical configurations containing straight portions are disclosed in U.S. Patents 2,637,893; 2,828,752; 2,939,201; and 2,317,- 485. It has been found however that previous departures from the conventional round cross section are not without adverse effects on processability, latent yarn bulking properties, or the response of the latent properties to finishing operations.

It is an object of this invention to provide a novel yarn having improved visual appearance.

It is another object of this invention to provide a textured continuous thermoplastic yarn having pronounced luster highlights and acceptable processability in carpet tufting operations and which, after incorporation into a textile structure, can be treated at elevated temperature so as to develop improved resiliency and covering power.

It is a further object of this invention to provide a process for the production of bulked polycaproamide yarns of novel cross sectional configuration useful in the production of tufted carpets which can be thermally treated to develop improved resiliency and covering power. Other objects and advantages will become apparent hereinafter.

It has now been found that filament cross sectional configurations which posses three lobes having a line of symmetry instead of a center of symmetry, and having the particular geometry below defined afford filaments of high bending modulus which, when provided with periodic sites of inter-crystalline strain and disorientation, exhibit a controlled increase in bulk in response to yarn relaxing conditions. By utilizing the effect of the special cross sectional configuration, in combination with other filament and polymer characteristics, I have found, a yarn is provided which not only processes well in tufting operations, but moreover produces carpet structures of good covering power, resiliency and improved luster highlight.

The invention will be better understood by reference to the drawings which illustrate preferred embodiments of the invention, and wherein:

FIG. 1 is a magnified sectional view of a trilobal filament in accordance with this invention. As shown in FIG. 1, the periphery of the cross section can be regarded as being formed from three circles centered at A, B, and C. In the figure, these circles are completed by dotted lines; and points of inflection on the periphery passing from one to the next cycle are indicated at A and A"; B and B"; C and C".

FIG. 2 is a magnified section of a multi-filament yarn of this invention, showing how the filaments pack together by reason of the particular cross section.

FIG. 3 is a plan view of a spinneret 1 suitable for producing the multifilament yarn of the invention.

FIG. 4 shows in sectional elevation a typical orifice of the spinneret, consisting of cylindrical inlet passage 2 leading to a group of three holes 3, forming an isosceles triangle.

FIG. 5 is an enlarged plan view showing the arrangement of holes 3 at the base of inlet passage 2, the apex hole of the isosceles triangle being at the center of pas sage 2. The centers of these holes are indicated at A, B, C to correspond with the centers of the lobes produced from the respective holes as indicated in FIG. 1.

Referring to FIGURE 1, the points A, B, and C represent the centers of curvature of the three individual lobes, the lobes centered at A and C having substantially the same radius of curvature (r); and that centered at B having radius of curvature from /2 to 2 fold r, and preferably about equal to r. The points A", B", and C", etc. define inflection points on the circular arc of each lobe. An inverse curvature is found between inflection point A'B, A" and C", and B" and C. For convenience of definition the lobe defined by center of curvature B may be referred to as the center lobe, and the other lobes will be referred to as pendant lobes. The lines of centers drawn between B and A, and between B and C are essentially equal in length and define the extension of the centers of the pendant lobes from the centerof the center lobe. This distance, for convenience of discussion, will hereinafter be referred to merely as the extension. The intersection of the extension lines defines the included angle alpha (or). The bisector line of angle (a) bisects the most pronounced of the three sectors of inverse curvature, A"C", and constitutes the axis of symmetry for the over-all configuration.

In accordance with this invention, a trilobal crosssection of a yarn filament as in FIGURE 1 is provided, having the three lobes separated by peripheral arcs of inverse curvature which arcs between the center lobe and pendant lobes are essentially identical and have larger radii of inverse curvature than does the arc between two pendant lobes; and wherein the angle (on) is between 80 and 120; the lobe radius, r, is generally, and especially for carpet yarn, in the range from about 5 to about 20 microns; the ratio of lobe radius to extension is between 0.60 and about 1; and the total circular arc AA", BB, CC" is between 400 and 800.

Among the filaments of a yam, the cross sections will vary more or less. I prefer that substantially all filaments of a single yarn of my invention have cross sections within the above ranges; and on the average have circular arc of about 400-600, and included angle (a), of about 90, and ratio of lobe radiuszextension of about 0.81.0, corresponding to the two pendant lobes being formed from overlapping circles and the center lobe being formed from a circle cutting about midway through the overlapping area of the other two circles, the three circles having substantially equal radii.

The measurements and geometry of cross sections of filaments in accordance with this invention can be obtained by measuring photornicrographs of sections of the filaments, at known magnification. The values referred to herein, unless otherwise specified, are to be understood as being average values, averaged over about 20 filaments of a cross section of a yarn.

The preferred carpet yarns of this invention are continuous textured multifilament thermoplastic yarns having the above described filament cross section, a total yarn denier between 2,000 and 4,500, individual filament denier between 7 and 25, packaged crimp index between 4% and 11%, and a relaxed crimp index between 8 and 15 percentage units greater than the packaged crimp index.

The crimped filaments of carpet yarn of the invention are characterized in having a zig-zag or saw-tooth type of crimp configuration consisting of crimp points between otherwise straight portions of filament. The crimp points, under polarized light, display a sharply defined strain zone. When successive cross-sections of filament are taken and examined by X-ray diffraction techniques, it is found that the X-ray pattern changes abruptly at the crimp point, where it becomes considerably more diffuse than in the straight portions, indicating a decrease in inter-crystalline orientation of at least about 20%. The frequency of occurrence of crimp points, and the average of the angle B determined by the straight sides (b) at crimp points (a) are definitive of the crimp characteristics of the fibers. The average number of crimp points per unit unextended length of fiber, and the average value of the angle B may be ascertained by microscopic examination. As a more convenient indication of crimp characteristics however, the crimp index method may be employed wherein a length of fiber is measured hanging under an added load of 0.1 gram per denier for a period of 2 seconds (length L under which condition the crimp aingle is fairly straightened to 180, and measuring the length of the same fiber hanging under no added weight after an elapsed time of at least 15 seconds from any previous stress (length L The crimp index is then calculated in accordance with the formula vention will undergo a permanent decrease in the angle B, and thus an increase in crimp index. It has been found that an increase in the crimp index of at least 8 percentage units is required to secure satisfactory resiliency and covering power in carpets, but crimp index increases greater than about 15% cause an undesirable matting effect. The increased value of the crimp index may be referred to as the relaxed crimp index. Relaxing conditions useful in increasing the crimp index of the yarns of this invention include conditions of zero yarn tension, elevated temperatures above the second-order glass transition temperature of the yarn, and preferably contact with plasticizing agents. Specific relaxing treatments include exposure of carpets to dry heat or steam, and immersion in hot aqueous scouring baths or dyebaths. Treatment temperatures between 125 C. and 250 C. may be employed for durations of several seconds to an hour, depending upon the nature of the yarn and other factors. Polycaproamide yarn is especially preferred in the practice of this invention in view of its good response to the relaxing conditions encountered in carpet finishing operations such as dyeing and steaming.

Although I do not wish -to be bound by theoretical explanations, it is felt that the novel cross-sectional configuration of this invention exerts a beneficial moderating effect on the forces at the filament crimp points which tend to contract the crimp angle upon exposure of the filaments to relaxing conditions. Thus, the filaments of this invention, having a line of symmetry in their cross-sectional configuration, undergo a smaller increase in crimp index upon relaxation than centrally symmetrical filaments having circular, Y-shaped, tri-lobal, or clover leaf configurations, and undergo a greater increase in crimp index than tri-lobal filaments having an angle (a) greater than The tri-lobal configuration imparts rigidity toward bending, and this rigidity translates into greater resiliency in the carpet structure. The rounded nature of the lobes permits the individual filaments to freely pass over one another and thereby intermingle with adjacent filaments to secure greater covering power during carpet after-treatment. The absence of sharply defined internal cusps or corners within the filament configuration of this invention, such as exists in ordinary three-leaf clover and Y-shaped configurations of the prior art, minimizes the tendency of the yarns of this invention to attract and hold dirt. The complete absence of straight portions in the cross-sectional configuration facilitates transient compaction of the filament bundle to enable passage through the narrow eye of a tufting needle. It is surprising that even though the filaments have no fiat surfaces, they afford a degree of luster highlight which surpasses angular, round, or centrally symmetrical trilobal filaments.

The yarn product of this invention may in general be prepared by melt extruding a thermoplastic polymer of fiber forming viscosity downward through spinnerette plates as illustrated in FIGURE 3 of the drawings, containing orifices as illustrated in FIGURES 4 and 5 of the drawings, consisting essentially of three closely positioned separate circular holes arranged in an isosceles triangle; and employing spinning conditions such that a controlled degree of coalescence of the three separate extrudate streams occur prior to solidification of the polymer.

The degree of coalescence of the three separate extrudates varies depending upon spacing of the three extrudates, spinning temperature, rate of extrusion, rate of extrudate cooling, viscosity of the extruded polymer. It will be appreciated, accordingly, that these factors must be maintained under close control to assure uniform results.

Spacing, over the critical portion of travel, is largely a matter of spacing of the holes; but also involves the socalled nodular effect, whereby a melt extruded under high pressure through a narrow passage tends to expand or thicken upon emergence from the passage. Cylindrical or slightly downward tapering holes are preferred. Holes with diameters between about 0.005 and about 0.02 inch and length between about 0.01 inch and about 0.05 inch are employed for production of carpet yarn. The separation between peripheries of the nearest adjoining holes is between 0.001 and 0.005 inch.

' Spinning temperature is suitably in the range 250- 285 C., preferably 255 275 maintained constant by jacketing the pack containing the filter and spinnerette.

Extrusion rate is controlled by a precision feed and take-up system, and cooling rate is controlled by a nonturbulent flow of constant temperature, constant humidity gas introduced into the spinning tower, especially air.

Polymer viscosity is a highly important factor and should be controlled within :2 units of Formic Acid Relative Viscosity, preferably within :1 unit. For polycaproamide, suitable polymer viscosities, as measured in terms of Formic Acid Relative Viscosity in aqueous 90% formic acid solution of 11 grams of polymer in 100 ml. solvent at 25 C. (ASTM procedure D789 53T) are between 30 and 75. The polycaproamide should contain not over 0.2% moisture and not over about 2% monomer.

The included angle (on) of the filament cross section of FIGURE 1 is determined by the corresponding angle between the centers of the three holes in the spinnerette orifice, which accordingly is between 80 and 120, especially about 90.

The extruded filaments are taken up under low tension not above about 0.1 gram per denier, to avoid undue stretching. Thereby the natural tendency under these spinning conditions of the molten filaments to thicken contributes to the desired quick, controlled coalescence. Over a first zone in the spinning tower, the freshly extruded filaments are contacted with a non-turbulent counter-current flow of air which causes their solidification at the exterior. This air acts to carry off monomer vapors from e.g. polycaproamide, thereby avoiding later difficulties which would develop from excess quantities of monomer in the polymer. This first zone will generally be about 3 inches to about 1 or 2 feet long, such as to complete or substantially complete the exterior solidification. The filaments will then pass into a non-turbulent stream of co-currently flowing gas, moving downward with at least twice the volumetric flow rate of the countercurrent stream of gas and Will be further cooled thereby over a length of travel at least five-fold the travel in the co-current gas stream.

The yarn thus prepared will be subjected to drawing operations, with or without application of heat, which orient the molecules of the polymer and thereby impart improved strength to the yarn.

To obtain the crimped yarn of my invention, the drawn yarn resulting from the above operations is subjected to a crimping operation which imparts to the filaments angular crimps, at temperatures not below 100 C. and not above the heating zone temperatures described below. Suitable crimping processes include stuifer-box methods such as described in Pike U.S. Patents 3,037,260 of June 5, 1962, and 3,031,734 of May 1, 1962; jet-impingement methods such as described in Hallden et a1. U.S. Patent 3,005,251 of October 24, 1961; belt or gear crimping processes such as described by Shattuck U.S. Patent 2,751,661 of June 26, 1956; and other processes analogous thereto.

The crimped yarn thus produced is then subjected to a stressing operation which imparts the latent contraction response properties to the yarn by a process wherein the crimped yarn is removed from the crimping chamber and cooled in relaxed form; the yarn is then tensioned to straighten it and passed through a heating zone maintained at temperatures above the second order transition temperature of the yarn, and preferably at temperatures within about 50 C., below the polymer melting point. For polycaproamide, the melting range is about 215- 6 225 C. The residence time of the yarn in this stressing zone is generally in the range of about 3 seconds to about 30 seconds. The yarn is subsequently cooled while still under tension such as to maintain its extended form.

The stressing process is generally found to aifect an average reduction in the crimp angle, B, of between 5 and 15. The yarn may subsequently be twisted, entangled, randomized, or sized prior to packaging. Various finish compositions may be applied to the yarn either prior or after crimping to facilitate the various textile operations.

In the absence of well recognized objective quantitative tests for the various desirable characteristics of floor coverings, the evaluation of the several advantages secured by the practice of this invention were found to be most reliably ascertained by a subjective rating system wherein 6 persons would study the same sample for same characteristic. Ratings were then made on a scale of from 1 to 5 with a rating of 5 representing a high degree of the desired property and a rating of 1 indicating an unsatisfactory level for that particular characteristic. The average value of the six persons would then constitute the rating of a particular property for a particular sample. In this fashion, ratings were made of such characteristics as luster highlights, covering power, resiliency, soiling propensity, and matting or pull down.

The following specific examples are given to illustrate preferred methods of carrying out the present invention. It is to be understood, however, that the examples are not to be considered as limitative of the scope of the invention. Percent in the examples means percent by weight in referring to concentrations.

Example 1 Polycaproamide polymer was used having a moisture content of 0.05 %0.10%, total constituents extractable by hot water of 1%-2%, and Formic Acid Relative Viscosity of 57. The polymer contained about 0.2% titanium dioxide dulling agent. The polymer was melted in a screw extruder, and the melt at 285 C. was forwarded at a pressure of 1800 psig through a sand filter to a spinneret plate upon which 70 three-hole orifices were arranged in 2 concentric circles, 30 in a 3 /2 inch diameter circle and 40 in a 4 /2 inch diameter circle, the 3 holes forming an isosceles triangle approximately bisected by the circle. The pack containing the filter and spinneret was jacketed with high boiling liquid (Dowtherm) held at contsant temperature of 257 C.

Each of the 70 orifices consisted of a cylindrical inlet passage about 1 A, inch deep and inch in diameter, leading to the groups of 3 holes, each of which was about 0.02 inch deep and about 0.014 inch in diameter. The 3 holes of each group formed an isosceles triangle with apex angle of and each leg 0.0165 inch long, leaving a separation of 2.3 mils (0.0023 inch) between the periphcry of the center or apex hole, and that of each of the outer holes.

The face of the spinneret was coated with a fluid polysiloxane release agent. The throughput was 32.5 lbs./ hr. of polymer. The freshly extruded filaments descended a spinning tower into which air at 82 F. and 65% relative humidity was admitted about 8 inches below the spinneret. The tower was 9 inches in diameter and 15 feet long. A minor portion (about /s) of the entering air was drawn upward as a non-turbulent stream in countercurrent contact with the descending filament; and the major portion of the entering air flowed downward as a non-turbulent stream in cocurreut contact with the descending filaments. The 3 filaments of each group partially coalesced and began to solidify, forming trilobal cross section, within one inch of the spinneret face. As the resulting coalesced filaments descended in the tower they further solidified, maintaining trilobal cross section.

The yarn emerging from the spinning tower contacted a ceramic roll which applied a lubricating finish, and

7 the yarn then passed to a driven roll and was convolutely wound onto a package at 1850 ft./ min. and tension of 90110 grams. The yarn thus obtained, having denier of 4080, was drawnover a /8 inch diameter drawpin at of the sample. The carpet sample was then evaluated for various characteristics.

Evaluation of soiling propensity was made based upon carpet samples which were carefully exposed to normal delivery rate 1536 ft./min. which was 3.7 times the feed usage within building corridors for a controlled extent of rate, to secure a drawn yarn denier of 1200 wherein each trafiic thereupon and determining the extent of soiling of of the 70 filaments had a denier of 17. During drawing, the sample in comparision with a sample of the original the yarn was passed in 5 wraps over a shoe-type heater carpet and samples of other carpeting fabricated to the maintained at 185-190 C. in accordance with Wincklsame general characteristics but made with round cross hofer U.S.P. 2,859,472 of Nov. 11, 1958. section filaments instead of the filaments of this invention. The trilobal cross section of the resulting yarn, on the Covering power was judged by visual determination of average, had included angle (a) of about 90; ratio of whether the white colored carpet backing could be seen lobe radius to extension of about 0.65, and about 750 through the pile surface when viewed from above. of lobe are. All lobes had substantially equal radii of The luster highlight rating was determined by inspection about 8.5 microns. of the carpet sample at a 45 angle in ordinary daylight, The yarn was then subjected to a continuous stuffer in comparison with control samples of round cross section box crimping operation employing apparatus essentially as fiber carpeting and centrally symmetrical trilobal cross described in Pike US. Patent 3,037,260 of June 5, 1962, section fiber carpeting. The carpet of this example and process conditions essentially as described in Pike showed in uniquely high degree a luster highlight U.S.P. 3,031,734, of May 1, 196 2. Specifically, 60 sepacharacterized by diamond-like sparkle crystals of light, rate ends of the above prepared yarn, combined into 20 conveying an appearance of depth by reason of the conthree-end groups, were continuously fed to a preheating trast of the sparkles against the darker surrounding backchamber containing superheated steam at a temperature ground. Luster highlight results from refraction of light of 172 C. The yarn emerging from the preheating chamrather than the simple reflection, which produces luster. her, at a temperature of about 140 C., was directly fed The evaluated characteristics of the carpet sample of as 20 three-end groups to the nip rolls of a crimper operthis example, in comparison with various control samples, ating with a nip roll pressure of 15 p.s.i.-g. and an exit are presented in Table I.

TABLE I [Property ratings] Sample Luster Resiliency Covering Soiling Highlight Power Resistance A Carpet of This Example .1 4. 5 4. 2 4.1 3.4 Round Filament Control 1 1. 2 1.6 3.2 4. 3 C Symmetrical Trilobal Control 3. 7 4.6 4. 4 3. 5 D Three-Leaf Clover Control 3. 3 3. 7 3.8 1.8 E Y-Shaped Control 3.6 4.0 3.8 3.4 F Fused d-Filament Control 1.6 2.0 3. 4 2.6

1 A carpet prepared as in this example employing yarn prepared in accordance with this example with the exception that the filaments have a circular cross-section.

' Same as 1 except that the filaments have a centrally symmetrical trilobal cross-section resembling Figure 2 of US. Patent 2,939,201.

3 Same as 1 except that the filaments have a centrally symmetrical three-leaf clover cross-section resembling Figure 2 of U.S. Patent 2,968,857

4 Same as 1 except that the filaments have a Y cross-section resembling Figure 1 of U.S. Patent 2,828,752. 5 Same as 1 except that the filaments consist of six circular filaments fused together resembling Figure 1 of 17.8. Patent 2,959,839.

gate pressure of p.s.i.g., and maintaining a temperature of about 125 C. in the crimping chamber. The yarn emerging from the stutfer box crimper was then cooled in compacted form to a temperature of 70 C. The 20 three-ply yarns were then separated and continuously forwarded through a stressing chamber containing steam at 1 p.s.i.g. at temperature of 175 C., and wherein the tension on each yarn end was 775 grams. The residence time of the yarn in the chamber was about 17 seconds. Upon emergence from the stressing chamber pull rolls, the yarn was tensioned to maintain the extended form while cooling, and the yarn was then wound convolutely onto tube supports. The packaged yarn had a denier of approximately 3 600 and consisted of 210 individual filaments. The yarn had a packaged crimp index of 6.7% and a relaxed crimp index, determined after subjecting a sample of yarn to boiling water for 1 hour under no tension, of 20.7%.

The packaged yarn thus prepared was employed in making a loop pile tufted carpet having 6 tufts per inch and 20 ounces of fiber per square yard of carpet, employing a woven jute backing of 12 ounces per square yard. The tufting needle had an oval shaped eye inch high and inch wide and operated at a rate of 520 tufts per minute. Performance of the yarn during the tu'fting operation Was excellent, without occurrence of any stoppages of operation due to the inability of the yarn to pass freely through the eye of the needle. A sample of the tufted carpet was then scoured at 212 F., dyed blue, and a standard latex dispersion was applied to the backing As the data of Table I indicate, filaments having a cross-sectional configuration within the purview of this invention exhibit a surprisingly high luster highlight, and good ratings of resiliency, covering power, and soiling resistance in comparison with previously known crosssectional configurations.

Example 2 In order to determine the effect of the ratio of lobe radius to extension on the characteristics of the filaments of this invention, a series of yarns were prepared utilizing the spinnerette and spinning conditions of Example 1 but employing polycaproamide polymers of various viscosities. It was found that the ratio of lobe radius to extension would increase with a decrease in the Formic Acid Relative Viscosity of the polymer employed. It was also found that, unless the polymer contained less than 0.2% moisture, unsatisfactory coalescence of the three extrudate streams would occur. The yarns thus prepared, all having an angle (a) of were crimped, stressed and woven into canpets in accordance with the method of Example 1. The nature of the samples prepared, and test results obtained therewith are presented in Table II.

As the data of Table 11 indicate, the ratio of lobe radius to extension is a critical parameter in the securement of the desired advantages of this invention. Ratios above about 1.0 result in diminished luster highlight, and an excessively high increase in crimp index upon relaxation which results in pull-down or matted carpet appearance. Ratios below about 0.60 also result in diminished TABLE II Polymer 4 Ratio of Luster Packaged Relaxed Percentage Sample Polymer 1 Moisture Lobe Radius Highlight Crimp Crimp Units Increase Viscosity Content to Extension Rating Index Index in Crimp (percent) Index 1 In units of Formie Acid Relative Viscosity.

2 Carpet sample exhibited undesirable pull-down and an unsatisfactory loft rating of 1.3. 8 Carpet sample exhibited unsatisfactory covering power rating of 1.5.

4 All polymer samples additionally contained 9.85% e-caprolactam.

luster highlight, and in addition have inadequate response 10 sq. yards of tufted carpet. Satisfactory operation is to TelaXing Conditions to Provide Satisfactory Covering generally considered to require less than 24 occurrences power. of stoppage or defects per 10 sq. yards. The nature of Example 3 the samples tested and the results obtained therewith are In order to determine the eifect of the angle 0: on the Presented Table All Y l Samples tested P characteristics of the filaments of this invention, a series turns P Inch Z tWI t, and ontalned equal quantities of of melt-spun yarns were prepared employing spinnerettes a standard mineral oil-based yarn lubricating finish.

TAB LE IV Cross Section 1 Sample Yarn Filament Packaged Tufting Carpet Quality 2 Denier Denier Crimp Index, Processability 0. Ratio Are 3 Percent 1, 200 12 90 0.85 425 8 4 Poor covering power.

2, 400 12 90 0.85 425 8 4 (1 Good.

8,600 12 90 0.85 4 5 8 4 .d0 Do.

4,800 12 90 0.85 425 8 4 Unsat1siact0ry Tufting defects.

3, 100 90 0.90 4 6 5 Fair Poor covering power.

2,400 5 90 0.80 450 10.4 Good Poor resiliency.

1 Cross-section of this invention corresponding to Figure 1, defined in terms of the angle P, the ratio of lobe radius to exrension, and the degrees of lobe are.

2 After finishing by the method of Example 1. a The lobe arc value is an approximate number due to the dlfliculty 1n ascertaimng the exact location of the SIX inflection points.

having various angles ea in the 3-hole patterns. Hole As the data of Table IV indicate, samplesU andVwithspacing and process conditions were carefully controlled ing the purview of the crimped carpet yarns of this inso as to secure a ratio of lobe radius to extension of ntion pr duce good tufting processability and good 0.690.74 for all samples prepared. The yarns were quality carpets. Sample T, having a denier below the evaluated on pirns for luster highlight. The nature of preferred range f this invention for crimped carpet the samples prepared, and test results obtained therewith y P c o pets having poor covering power; and are presented in Table III. sample W, having a denier above the preferred range,

TABLE III performs unsatisfactorily in the tufting operation. Samples X and Y illustrate the effects of filament deniers,

Angle Luster above and below the preferred range respectively. The

Sample Polymer (a), Highlight data in general illustrates the critical requirements of Rating yarn and filament denier characteristics in the securement of crimped carpet yarns which not only process well but it; fi ii i ffiffifi fji::::::::::::::::: 33 iii also yield good quality carpets- N Poly(hexamethylene adipamide) 115 4.2 In order to secure a satisfactory increase in crimp g 5. 513 3 7 iH-deX f between 8 and 15 percentage units upon ex- 0 do 115 4.2 posure of the yarn to relaxing conditions, it is essential 313:: iflfifigifififi'fff ifl agj 5; that the yarn contain the angular crimps prescribed herein containing sharply defined internal strains as may be detected by polarized light, and crystalline disorientation at the crimp points detectable by X-ray diffraction. Although ordinary crimping processes such as the stutterbox method will provide angular crimps, these methods generally do not impart suitable internal strain at the crimp points. By the process of this invention internal strain is imparted to the angular crimps by a thermal stressing operation involving controlled conditions of temperature, time and stress. Although the theoretical factors underlying the stressing operation are not clearly understood, it is felt that the polymer in the periphery of the fiber at the crimp point becomes plasticized, enabling the fiexural widening of the angle B by the tension As the data of Table III indicate, the unexpected criticality of the angle on is such that angles outside the range of 80120 of this invention produce an unmistakably diminished luster highlight rating. Thus, samples L, P, and R, which are outside the scope of this invention, are generally characterized in having luster highlight ratings below about 4. The data of Table III is also noteworthy insofar as it establishes that the desirable quality of luster highlight is dependent upon the novel configuration of the filament and that factors such as polymer type, crimp characteristics, and fabric construction are not controlling on this characteristic.

Example 4 applied to the yarn. Upon emergence from the heated The processability f yarn in t f i operations was stressing zone under tension, the peripheral polymer redi d employing h t -fti di i f Example 1 hardens and, thereby encases or freezes-in the internal on various polycaproamide yarn samples. As -a measure strain or mechanical POE"ntial energy at the Crimp P of processability, the number of stoppages or quality de- Upon su'bsequent'exposure of the stressed yarn thus prefects due to the behavior of the yarn was counted per pared to relaxing temperatures, the peripheral polymer layer will again become plasticized and under the zero tension of relaxation enables the internally strained portion to return to an unstrained condition. The effect is thereby analogous to a stretched spring which, upon removal of restraining forces, returns to its original length.

Although the combination of the novel cross-sectional configuration of this invention with angular strained crimps in a thermoplastic fiber affords unexpected synergistic improvements in the production of floor coverings, filaments having the cross-sectional configuration of this invention are useful in numerous other textile applications in staple and continuous filament homofiber and blends in uncrimped or crimped form. In view of the desirable aesthetic qualities of luster highlight imparted by the fiber, typical textile applications would include apparel products such as woven suitings, shirtings, sheeting and lingerie, tricot, circular knitted fabrics, broadcloths, satins, and the like. In view of their relatively high surface area, stiffness, and strength, the filaments of this invention are useful in industrial textile applications such as sewing thread, fiber-reinforced laminates, tire cord, upholstery, drapery, curtains, ducks, and other applications.

The yarns may be made to contain various additive ingredients which impart specialized properties. For example, ingredients which may be added to the yarn either by incorporation within the polymer prior to spinning, or by after-treatments of the yarn or fabric include flame retardant agents such as compounds of antimony, phosphorous, and halogens; titanium dioxide delusterant; antistatic agents; adhesion promoting agents such as isocyanates and epoxides; heat and light stabilizers such as inorganic reducing ions, metal ions such as manganese, copper and tin, phosphites, and organic amines such as alkylated aromatic amines and ketone-aromatic amine condensates; thermally stable pigments such as Quindo Magenta (Allied Chemical Corp.) and inorganic pigments; fluorescent agents and brighteners such as Tinopal 'POR; cross-linking agents; bacteriostats such as phenols and quaternary amines; colloidal reinforcing particles; antisoiling coatings such as colloidal silica and boehmite; and other known additives and treatments. It is essential however, that essentially no volatile ingredients such as water or solvents be contained by the polymer prior to extrusion since these are deleterious to satisfactory extrudate coalescence. The presence of plasticizers however are beneficial to extrudate coalescence, and can be removed if desired after filament formation. In the case of polycaproamide polymer, the presence of about 0.5%- 2% of monomeric lactam which acts as a plasticizer, facilitates extrudate coalescence, and this represents a highly preferred aspect of the present invention.

Thermally stable flow controlling agents or surfaceactive agents which decrease surface free energy may be included within the polymer prior to extrusion to increase the extent of extrudate coalescence, and thereby increase the ratio of lobe radium to extension. Examples of such agents include: metal salts of long chain aliphatic carboxylic acids, long chain aliphatic alcohols, long chain aliphatic amides, and fluorinated and other surface active agents.

The yarns of this invention can be admixed with yarns of round cross section or of various modified cross sections, of the same or different denier and of the same or different chemical composition to produce various special effects.

As many widely different embodiments may be employed or made without departing from the spirit and scope of this invention, it is to be understood that the invention is to be in no wise restricted save as set forth in the appended claims.

I claim:

1. A process for the production of polycaproamide yarn comprising extruding downward at constant temperature between about 250 C. and about 285 C. e-polycaproamide having constant Formic Acid Relative Viscosity between about 30 and about i2 unit, containing not over about 2% of monomer and not over 0.2% moisture through a plurality of spinnerette orifices, each orifice consisting of an inlet passage leading to a group of three circular holes, said three holes arranged with their centers forming an isosceles triangle having apex angle in the range of about to about 120, the separation between peripheries of the nearest adjoining holes being in the range of about 0.001 to 0.005 inch; and contacting the extruded polycaproamide filaments with a non-turbulent stream of gas while the filaments are under low take-up tension not greater than about 0.1 gram per denier based on denier of the yarn as taken up, until the three filaments of each group coalesce and solidify, to produce trilobal cross section.

2. Process of claim 1 wherein the spinning temperature is in the range 255-275 C.; the three orifice holes of each group have the same diameter in the range from about 0.005 to about 0.02 inch and their centers form an isosceles triangle with apex angle of about the freshly extruded filaments travel in a counter-current gas stream between about 3 inches and about 1 foot, and then travel in a cocurrent gas stream moving downward with at least twice the volumetric flow rate of the countercurrent stream of gas, over a length of travel at least five-fold the travel in the counter-current gas stream; and the gas used is air introduced at constant temperature and humidity into the spinning tower.

3. Process comprising imparting to the yarn resulting from the process of claim 2 an angular crimp at temperatures not below C. and not above the heating zone temperature specified below; cooling the crimped yarn in relaxed form; tensioning the resulting yarn to straighten it and passing the straightened yarn through a heating zone maintained at temperatures within about 50 C. below the polymer melting point; and then cooling the yarn.

References Cited by the Examiner UNITED STATES PATENTS 2,804,645 9/ 1957 Wilfong. 2,939,201 6/1960 Holland 18-8 X 3,216,186 11/1965 Optell. 3,257,487 6/1966 Dulin 264-176 ALEXANDER H. BRODMERKEL, Primary Examiner.

I. H. WOO, Assistant Examiner. 

1. A PROCESS FOR THE PRODUCTION OF POLYCAPROAMIDE YARN COMPRISING EXTRUDING DOWNWARD AT CONSTANT TEMPERATURE BETWEEN ABOUT 250*C. AND ABOUT 285*C. E-POLYCAPROAMIDE HAVING CONSTANT FORMIC ACID RELATIVE VISCOSITY BETWEEN ABOUT 30 AND ABOUT 75 $2 UNIT, CONTAINING NOT OVER ABOUT 2% OF MONOMER AND NOT OVER 0.2% MOISTURE THROUGH A PLURALITY OF SPINNERETTE ORIFICES, EACH ORIFICE CONSISTING OF AN INLET PASSAGE LEADING TO A GROUP OF THREE CIRCULAR HOLES, SAID THREE HOLES ARRANGED WITH THEIR CENTERS FORMING AN ISOCELES TRIANGLE HAVING APEX ANGLE IN THE RANGE OF ABOUT 80* TO ABOUT 120*, THE SEPARATION BETWEEN PERIPHERIES OF THE NEAREST ADJOIN- 